This invention generally relates to plastic extrusion blow molding machines and particularly concerns a quick change system and method for interchanging molds on platens of different blow molding machines.
Different molds have long been interchanged on basic plastic extrusion blow molding machines in a time consuming, laborious process. These machines are often customized and use molds which comprise an assembly of parts which normally remain together as an operative unit. That is, each time a conventional new mold is purchased, associated parts such as a back plate and a water manifold for supplying coolant water are provided for that new mold so as to permit the parts to be installed and later removed as an operative unit. Another part required for that new mold is a detabber. As is well known to those skilled in the art, in such blow molding machines, a tab of plastic (attached to a base of a blow molded object such as a container) is formed and must be removed prior to completion of the molding process. A detabber having a stripper bar which has been previously used with success is shown in U.S. Pat. No. 4,419,063 assigned to the assignee of this invention. The stripper bar is power operated to pivot against a mating fixed stripper plate for removing the tab from the molded object.
A series of heretofore unsolved problems are associated with the changing of a mold in a plastic extrusion blow molding machine. These problems involve the disassembly of water hoses from their connection on a side of the back plate and the disassembly of air feed hoses to the detabber, in addition to the removal of operative parts from the extrusion blow molding machine whereby the highly labor intensive, critical alignment of the mold to that machine is lost. To remove one mold and attach a new mold thus may take as long as three hours in disassembly of one mold from the machine, including disconnecting the water hoses and air feed hoses for respectively delivering required water to the blow mold and motive air power to the detabber, and then aligning a new mold to the machine, and again establishing the necessary fluid connections to the water manifold and the detabber.
Accordingly, an object of this invention is to provide a new and improved method which is particularly suited for expeditious changeover of an extrusion blow molding machine from one mold to another in a significantly reduced amount of time and which additionally provides notable cost savings in both ease of the manufacture and in minimizing the number of required operative component parts.
Other objects will be in part obvious and in part pointed out more in detail hereinafter.
This invention features a quick change method for interchanging molds on platens of different extrusion blow molding machines. A subplate dimensioned and configured for use with different blow molding machines serves as a universal standard component which may be permanently secured to a platen of a blow molding machine. The standard subplate has alignment means for positioning it in predetermined precision alignment with the machine platen. A plurality of different mold units are interchangeably attachable to the standard subplate. Each mold unit is mounted in a predetermined leveled and centered operating position on the standard subplate which establishes a preselected, precisely aligned relation between the installed mold unit and the machine platen. A water manifold and detabber are mountable on each of the different mold units as a unitary standard assembly with fluid connections for connecting the water manifold and the detabber respectively with water and air supply sources. During detachment of the standard assembly from a mold unit, the fluid connections between the fluid supply sources and the water manifold and detabber of the standard assembly are continuously maintained without being disconnected, thereby expediting mold change.